Sorry about the missive on 105mm SABOT. I'm a 120mm Master Gunner. All I know is that on the US M60A3 tank (105mm) sabot had a spin to it.

As for the 30mm and below question, I had a buddy that took small arms fire in Desert Storm, 7.62mm, nothing spectacular, and he said they could hear it on the side of the tank, like somebody hitting the side of the tank with a very small ball peen hammer.